Air loaded papermaking machine headbox with stock overflow channels and vertically aligned vanes therein

ABSTRACT

An air loaded headbox for a papermaking machine having an air chamber above vertical rectangular guide vanes defining top open channels between adjacent vanes. The vanes define a first plurality of the channels with end portions open horizontally to provide for horizontal stock flow therethrough. The vanes define a second plurality of channels with bottom portions open in a vertically downward direction to provide for skimming the upper surface of stock in the headbox by providing for a vertically downward stock overflow from the tops of the open tops of the horizontal stock flow channels, downwardly through overflow channels to an overflow collection chamber beneath the vanes. The channels are arranged with alternate horizontal stock flow channels and stock overflow channels across the width of the headbox. A pair of spacers is arranged between vanes defining a stock overflow channel, with each overflow channel spacer being adjacent an end portion of adjacent vanes and extending vertically between top and bottom positions of the adjacent vanes. A group of three spacers is arranged between adjacent vanes defining a horizontal stock flow channel. A first spacer of the group of three, extends horizontally between front and rear wall assemblies of the headbox and provides a floor for the horizontal stock flow channel. The second and third spacers of the group of three are horizontally spaced apart with each adjacent an upper end of adjacent vanes.

United States Patent DeNoyer 1 May 9, 1972 [5 AIR LOADED PAPERMAKING[57] ABSTRACT MACHINE HEADBOX WITH STOCK An air loaded headbox for apapermaking machine having an OVERFLOW CHANNELS AND air chamber abovevertical rectangular guide vanes defining VERTICALLY ALIGNED VANES topopen channels between adjacent vanes. The vanes define a THEREIN firstplurality of the channels with end portions open horizontally to providefor horizontal stock flow therethrough. The [72] Inventor Donald DeNoyerBelem vanes define a second plurality of channels with bottom por- [73]Assignee: Allis-Chalmers Manufacturing Company, tlons open in avertically downward direction to provide for Milwaukee, Wi skimming theupper surface of stock in the headbox by providing for a verticallydownward stock overflow from the tops of [22] Filed 1970 the open topsof the horizontal stock flow channels, [21 Appl. No.: 87,381 downwardlythrough overflow channels to an overflow collection chamber beneath thevanes. The channels are arranged with alternate horizontal stock flowchannels and stock over- ..162/337, l62/340b; f2/13/32 flow channelsacross the width of the headbox A pair of spacers is arranged betweenvanes defining a stock overflow [58] new of Search 1 62/343 3 3gchannel, with each overflow channel spacer being adjacent an end portionof adjacent vanes and extending vertically between top and bottompositions of the adjacent vanes. A [56] References cued rou of three sacers is arran ed between adjacent vanes g P P 8 UNITED STATES PATENTSdefining a horizontal stock flow channel. A first spacer of the group ofthree, extends horizontally between front and rear 3216392 1 H1965wahlstrm et "162/343 wall assemblies of the headbox and provides a floorfor the 35321598 10/1970 Lee et l "162/343 X horizontal stock flowchannel. The second and third spacers of lgog'lso 5/1933 Ben'lfvmg at162/343 X the group of three are horizontally spaced apart with each ad-3,092,539 6/1963 Schmidt et al. ..162/337 x V jacem an upper endadjacent Vanes 3,536,581 10/1970 Wolf ..l62/337 2,736,247 2/1956Hornbostel ..l62/34O Primary ExaminerS. Leon Bashore AssistantE.\'aminer--Richard H. Tushin A!l0rneyArthur M. Streich, Robert B.Benson and John P. Hines 12 Claims, 6 Drawing Figures AIR LOADEDPAPERMAKING MACHINE I-IEADBOX WITH STOCK OVERFLOW CHANNELS ANDVERTICALLY ALIGNED VANES THEREIN CROSS REFERENCE TO RELATED PATENTAPPLICATION This application discloses several keys and keyways, certainof which, but not all, are the subject of my copending U.S. patentapplications entitled Paperrnaking Machine Headbox Having VerticallyAligned Vanes Therein, Ser. No. 87,378 and An Air Loaded Headbox for aPapermaking Machine Having Vertically Aligned Vanes Therein, Ser. No.87,384, filed concurrently with this application.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to the construction of a headbox for spreading dilute paperstock across the entire width of a paper web former and particularly toa construction that may be applied with particular advantage to a verywide headbox for high speed web formation, which may be air loaded, andwhich provides for skimming off the upper surface of stock in theheadbox.

2. Description of the Prior Art Foaming on the free surface of the stockoccurs in headboxes of papermaking machines, in particular in the caseof sized paper stock suspensions, and leads to accumulations of foam.These foam accumulations may increase in height at the front wall of theheadbox clue to stagnation in the flow of the suspension and thus form aheap of foam which causes an undesirable lump formation in thesuspension immediately beneath the heap. From time to time these lumpswill drop to the headbox discharge outlet thus carrying batches of thefoam onto the wire, thereby bringing about irregularities in theformation ofthe web and breaks in the web.

Various methods have been suggested in the papermaking art with a viewof eliminating this foam formation. Thus, water was to be sprayed ontothe suspension in finely distributed jets by means of spray nozzles.Only fresh water can be used for this purpose, since white water fromthe white water pit of the machine would soon clog the narrow openingsof the nozzles. However, in stock inlets operated with air loading andhaving a relatively low depth of the suspension, and wherein the flow ofthe stock extends over the whole width and depth of the latter, the useof fresh water leads to a variation in the stock consistency at thesurface of the latter. The sprayed-on freshwater layer which thus tendsto form, is carried along by the flow of the stock without properlymixing with the suspension on the short way to the headbox dischargeoutlet, and thus disturbs the web formation and leads to anunsatisfactory look-through of the paper.

It is furthermore known to provide an overflow in the headbox in thevicinity of the rear wall of the latter, close to the entrance for thesuspension into the headbox. This overflow serves to control the stocklevel in the headbox but is not suitable for a withdrawal of appreciablefoam accumulations from the headbox. Indeed, it would not be possible toremove foam in substantial amounts by means of this known overflow evenwhen applying special foam dispersing means, since these foamaccumulations tend to move with the stock in the main direction of flowof the latter toward the discharge outlet for the suspension from theheadbox, and thus move away from the rear wall of the latter.

It is also known, as shown in U.S. Pat. No. 3,092,539 of I963 to providean overflow in the headbox in the vicinity of the headbox front wall.Such an overflow serves to skim off foam where it accumulates at thefront wall but does nothing to reduce the tendency for the foam toaccumulate at the front wall.

As will appear from the description to follow, the present inventioninvolves generally rectangular stock flow channel defining vanes whichare relatively thin, and arranged in a vertical position to present agreater horizontal length than vertical height. The vanes are paralleland closely spaced to define both horizontally extending stock flowchannels between adjacent vanes and stock skimming overflow channelsextending substantially the full length of the headbox between rear andfront wall assemblies. Vanes, for other purposes and without certainnovel features which will appear as the description of the presentinvention proceeds, are known and disclosed in U.S. Pat. Nos. 1,909,150(see FIG. 4) and 3,216,892 (see FIG, 1).

SUMMARY OF THE INVENTION The present invention applies to a headbox fora papermaking machine having a stock flow chamber between a verticalfront wall assembly, and a vertical rear wall assembly. A structuredefining a stock inlet chamber communicates through the rear wallassembly and a structure defining a stock outlet chamber with a sliceopening communicates through the front wall assembly. A plurality ofparallel and vertical guide vanes are arranged to define open topchannels extending from the inlet chamber to the outlet chamber. Each ofthe vanes are generally rectangular.

It is an object of the present invention to provide a new and improvedheadbox of the aforesaid type with provision for skimming the surface ofstock in the channeled headbox along substantially the full length ofthe headbox between rear and front wall assemblies.

It is another object of the present invention to provide a new andimproved headbox of the aforesaid type with provisions for minimizingdeflection of the front wall assembly and slice defining structure.

It is also an object of the present invention to provide a new andimproved headbox of the aforesaid type in which transverse deflection,that is deflection across the span of the box width, is both minimizedand independent of the dimension of the span of box width and/or machinespeed.

It is another object of the present invention to provide a new andimproved headbox adapted for changing open area of pulp stock flowchannels and/or stock skimming overflow channels without a need torebuild the walls and structures defining the box.

The improvement according to the present invention comprises providingthe vanes which define a first plurality of the channels with endportions open horizontally to provide for horizontal stock flowtherethrough and at least one overflow stock channel or preferably apluralityof second channels with bottom portions open in a verticallydownward direction to provide for skimming the upper surface of stock inthe headbox by providing for a vertically downward stock overflow fromthe open tops of the horizontal stock flow channels downwardly throughoverflow channels to an overflow collection chamber beneath the vanes.The channels are arranged with alternate horizontal stock flow channelsand stock overflow channels across the width of the headbox. A pair ofspacers is arranged between vanes defining a stock overflow channel witheach overflow channel spacer being adjacent an end portion of adjacentvanes and extending vertically between top and bottom portions of theadjacent vanes. A group of three spacers is arranged between adjacentvanes defining a horizontal stock flow channel. A first spacer of thegroup of three, extends horizontally between front and rear wallassemblies of the headbox and provides a floor for the horizontal stockflow channel. The second and third spacers of the group of three arehorizontally spaced apart and adjacent an end portion and the topportion of adjacent vanes.

A preferred embodiment may further provide horizontal structure spacedabove the vanes to enclose the chamber above the channelized flowpassages for air loading the stock in the open top channels with greaterthan atmospheric air pressure. The air pressure acts to apply outwardlydirected forces upon the front and rear vertical wall assemblies but thevanes tie the front and rear walls together to resist deflection causedby such forces.

Other features and objects of the invention that have been attained willappear from the more detailed description to follow with reference to anembodiment of the present invention shown in the accompanying drawing.

BRIEF DESCRIPTION OF THE. DRAWING FIG. 1 of the accompanying drawing isa view in perspective and in section, showing a papermaking machineheadbox according to the present invention;

FIGS. 2 and 3 are views taken along lines IIII and IIIIII, respectivelyin FIG. 1 and viewing the structure in the direction indicated byarrows; and FIGS. 4, 5 and 6 are views taken along lines IVIV, VV andVIVI respectively in FIG. 2 and viewing the structures in the directionindicated by arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a headbox10 is shown which comprises a stock fiow chamber 11 defined by verticalfront wall assembly l2 and a vertical rear wall assembly 13. If it isdesired to air load the chamber 11 with above atmospheric air pressure,a horizontal structure defining a box top 15 is also provided having aport 16 for devices (not shown) such as are disclosed in US. Pat. Nos.2,736,246 or 3,515,635. A structure defining a stock inlet chamber 17communicates with chamber 11 through an opening 18 in the rear wallassembly 13, and a structure defining a stock outlet chamber 19communicates with chamber 1 1 through an opening 20 in the front wallassembly 12. The stock flow chamber 11 is provided with a plurality ofparallel and vertical guide vanes 23. The vanes 23 define a firstplurality of channels 27 with end portions open through the openings 18and 20 to provide for stock flow therethrough. The vanes 23 which definethe channels 27 are spaced apart by a group of three spacers comprisinga first spacer 24, a second spacer 25, and a third spacer 26, to definechannels 27 with a top portion open to chamber 11. Each of the vanes 23are generally rectangular and (see FIG. 5) have a pair of vertical edgeportions 28 and 29, and a pair of horizontal edge portions 30 and 31.The vanes 23 also define a second plurality of channels 32 having a pairof spacers 33 and 33a between certain adjacent vanes 23 as will be morefully described later with reference to FIGS. 3 and 6.

. With continued reference to FIG. 1, the headbox 10 is provided with astock entrance assembly 34 which includes a manifold 35 with a pluralityof tubes 36 connecting manifold 35 to the inlet chamber 17. Theheadbox10 is also provided with a stock discharge assembly 38 which includes atop slice lip 39 connected to the front wall assembly 12 by a pivotalconnection 40 at the level of the top of opening 20 in the front wallassembly 12, and a bottom slice lip 41 connected to a lower front wallmember 42 which is part of the front wall assembly 12 at the level ofthe bottom of the opening 20. The top slice lip 39 and bottom slice lip41 define a slice opening 43 for discharging dilute paper stock onto aFourdrinier web forming wire 44 looped over a breast roll 45.

Referring to FIG. 5, each vane 23 is provided with a first key 51projecting vertically upward from the upper horizontal edge portion 30of vane 23 in a vertical plane adjacent edge portion 28. Each vane 23 isalso provided with a second key 52 projecting vertically upward from theupper horizontal edge portion 30 of vane 23 in a vertical plane adjacentthe other vertical edge portion 29. Each vane 23 is also provided withthird and fourth keys 51a, 52a projecting downwardly in verticalalignment with the keys 51, 52. Each vane 23 is provided with a fifthkey 53 projecting horizontally outward and away from the upper end ofthe vertical edge portion 28. Each vane 23 is further provided with asixth key 54 projecting horizontally opposite key 53 and in the samehorizontal plane with key 53. Each vane 23 is also provided with aseventh key 55 and an eighth key 56 projecting horizontally outward ofvane 23 in opposite directions along the lower horizontal edge 31.

Referring again to FIG. I, a first land 58 is connected to an uppermember 59 of front wall assembly 12 on the same side of wall assembly 12as the channels 27. The land 58 is spaced away from member 59 andprojects downwardly a predetermined distance to define a first keyway6(1extending upwardly a predetermined distance away from the channels27. A second land 61 is connected to an upper member 62 of the rear wallassembly 13, and on the same side of wall 13 as the channels 27. Theland 61 is spaced away from member 62 and projects downwardly apredetermined distance to define a second keyway 63 extending upwardly apredetermined distance away from the channels 27. A third land 58a isconnected to a lower member 59aof front wall assembly 12 on the sameside of member 59a as the channels 27. The land 58a is spaced away frommember 59a and projects upwardly a predetermined distance to define athird keyway 600. A fourth land 61a is connected to a lower member 620of the rear wall assembly 13 on the same sideof the wall 13 as thechannels 27. The land 61a is spaced away from the member 62a andprojects upwardly to define a fourth keyway 63a. A first horizontalshelf 65 projects, from another upper member 66 of the front wallassembly 12, inwardly and below the member 59 and toward the chamber 11and defines a fifth keyway 67. A second horizontal shelf 68 projectsfrom another upper member 69 of the rear wall assembly 13 inwardly belowthe member 62 and toward the chamber 11 and defines a sixth keyway 70facing and in register with the keyway 67. A third horizontal shelf 71projects from the lower front wall member 42 inwardly above member 59aand toward chamber 11 and defines a seventh keyway 72. A fourthhorizontal shelf 73 projects from a lower member 74 of rear wallassembly 13 inwardly above member 62a and toward chamber 11 and definesan eighth keyway 75.

As shown in FIG. 1, spacers 24, 25, and 26 are arranged against anadjacent vane 23 to space therefrom another vane which engages thespacers 24, 25, and 26 in a manner shown in FIG. 2, to define thechannels 27.

Referring to FIG. 4, the first spacer 24 is shown as having horizontaland oppositely projecting keys 81, 82 for projecting into keyways 72 and75 respectivelyand between vane keys 55, 56 respectively. The firstspacer 24 also has keys 81a, 82a projecting downwardly for projectinginto keyways 60a, 63a

respectively and between vane keys 51a, 52a respectively; The

first spacer 24 also has a midportion 83 between the keys 81, 82 thatprojects vertically upward a predetermined distance to define a floor 84for a channel 27. The second spacer 25 is shown as having a vertical key85 projecting upward into the keyway 60 between vane keys 51 and a key86 for projecting horizontally into the keyway 67 between vane keys 53.The third spacer 26 has a vertical key 87 for projecting upward into thekeyway 63 between vane keys 52, and a key 88 for projecting horizontallyinto the keyway 70 between vane keys Referring to FIG. 6, the pair ofspacers 33, 33a are shown which cooperate with adjacent vanes 23 todefine the overflow stock channels 32. The spacer 33 is shown as havingvertical keys 90, 91, horizontal keys 92, 93 and a midportion 94 with aninwardly facing wall 95 that provides one end wall for an overflowchannel 32. The spacer 33a has vertical keys 90a, 91a, horizontal keys92a, 93a and midportion 94a with a surface 95a providing another endwall for an overflow channel 32. The spacer keys 90, 91, 92, 93 abutvane keys 51, 51a, 53 and 55 respectively in keyways 60, 60a, 67 and 72respectively. The spacer keys 90a, 91a, 92a, 93a abut vane keys 52, 52a,54 and 56 respectively in keyways 63, 63a, 70 and 75 respectively.

As shown in FIG. 2, the vanes 23 define alternating channels 27, 32 withalternating and side abutting downwardly projecting keys 81a, 51a, 91,lower horizontal keys 81, 55, 93, upper horizontal keys 86, 53, 92, andupwardly projecting keys 85, 51, 90, all projecting into theirrespective keyways. Since the second and third spacers 25, 26 (as shownin FIG. 1 and FIG. 4) do not extend the entire distance between thefront and rear walls 12, 13, the channels 27 are provided with open topsas shown in FIG. 3, and since the pair of overflow stock channel spacers33, 33a are horizontally spaced apart as shown in FIG. 6 the overflowchannels 32 are open at both the top and the bottom as shown in FIG. 3.

As shown in FIGS. 4, 5, and 6, the vanes 23, the group of three spacers24, 25, 26, and pair of spacers 33, 33a, may be provided with holes 108for aligning rods (not shown) which may be used to hold these elementsin place during assembly and prior to securing them in the positionswhich have been described. All of the keys are tightly secured inkeyways in a manner that will be described next.

Referring again to FIG. 1, the shelves 65 and 68 have been described asbeing connected to and part of the wall assemblies 12, 13 respectively.The lower shelf 71 is part of the front wall assembly 12 as has beendescribed. The front wall assembly 12 also includes vertical member 96.Member 59a is connected on its upper end to a horizontal member 97 whichis also connected to the upper end of member 96. The lower front wallmember 42, from which the shelf 71 projects, is carried on top of themember 97. The member 42 is connected to the member 97 by screws 98which also serve to pull the shelf 71 downwardly to clamp the vane keys55 and spacer keys 81, 93, between the shelf 71 and the member 59a, Theupper part of the front wall assembly 12 includes the vertical members59,66, with the member 59 carrying the box top and defining the land 58and the keyway 60. The shelf 65 is connected to the member 66 in amanner which has been described. Bolts 99 are provided to draw themembers 59 and 66 together. The lower part of the rear wall assembly 13includes a vertical member 62a and the vertical member 74 and aspreviously described the member 74 supports the shelf 73. Bolts 100 areprovided to draw the members 62a, 74 together. The upper part of therear wall assembly 13 includes the vertical member 62 which carries therear end of the box top 15 and defines the land 61 and keyway 70, andthe vertical member 69 which carries the shelf 68. Bolts 101 areprovided to draw the members 62, 69 together. Jack screws 102, 103, and104 are also provided to secure the assembly in a manner which will nowbe described. Jack screw 102 is threaded in a portion of the member 66that projects over the top of the member 59. When the jack screw 102 isturned to move downwardly it engages the top of member 59 and the member66 is drawn upwardly an amount permitted by a loose fit of bolt 99throughthe members 59, 66 and as member 66 moves upwardly the shelf 65is pulled up to clamp the vane keys 53 and spacer keys 86 and 92, in thekeyway 67 and the vanes are placed in vertical tension between keys 53and 55 when the headbox is pressurized. Jack screw 103 is threaded in aportion of the member 74 that projects under member 62a. When jack screw103 is turned to move upwardly it engages the bottom of member 62a andthe member 74 and the shelf 73 are pulled downwardly an amount permittedby a loose fit of bolts 100 through the members 74, 62a and as member 74moves downwardly the shelf 73 is pulled downwardly against the vane keys56 and spacer keys 82, 93a in the keyway 75. Jack screw 104 is threadedin a portion of the member 69 that projects over the top of the member62. When jack screw 104 is turned to move downwardly it engages the topof member 62 and the member 69 is drawn upwardly an amount permitted bya loose fit of bolts 101 through the members 62, 69 and as member 69moves upwardly the shelf 68 is pulled up to clamp the vane keys 54 andthe spacer keys 88, 92a in the keyway 70 and the vanes are placed invertical tension between keys 54 and 56 when the headbox is pressurized.

The members 59 and 62 below the box top 15 cooperate with end walls (notshown) and enclose the chamber 11 above the open top channels 27.Pressurized air may be admitted to the chamber 11 through port 16 toload the stock in the open top channels 27 with above atmospheric airpressure. The members 62a and 59a spaced below vanes 23 cooperate withend walls (not shown) and a box floor 105 to provide an enclosed chamber106. A drain 107 may be provided for draining overflow stock fromchamber 106 to a white water pit (not shown) beneath the machine.

In the operation of the described apparatus dilute paper stock entersthrough manifold 35 and flows upwardly through the tubes 36 to the inletchamber 17. From the inlet chamber 17 the stock flows through thechannels 27 defined within the flow chamber 11 and stock rises upwardlyin channels 27 to a degree permitted by the pressure of air admittedthrough port 16. As the stock rises above vanes 23 the upper surface ofthe stock is skimmed off and overflows downwardly through the overflowstock channels 32 to chamber 106 and out drain 107. The weight andpressure of stock in such as the flow chamber 11, normally, in boxesconstructed according to the prior art, exerts forces tending to cause aheadbox floor to deflect downwardly across both the longitudinal andcross-machine spans of chamber 11. Furthermore, the pressure of thestock and air loading in such as the flow chamber 11 normally, in boxesconstructed according to the prior art, tends to deflect the front wall12 and stock discharge assembly 38 outwardly toward the slice opening43. With the construction that has been described however, the vanes 23are keyed and tensioned in keyways 67, 72, 70, 75 and the spacers 24 arekeyed in keyways 72, 75 for support by the front and rear wallassemblies 12, 13 to divide the cross-machine span into a plurality ofvery narrow cross-machine spans that have much less tendency forcross-machine deflection as a result of the vanes being supported ateach end and the resistance to deflection provided by vertical tensionapplied to the vanes when the headbox is pressurized. By providing thevertical vane keys 51, 51a and 52, 52a arranged as described, the vanes23 tie together the front and rear wall assemblies 12, 13 and minimizeoutward deflection of the front wall 12 and stock discharge assembly 38toward the slice opening 43 when the headbox is pressurized.

Thus it has been disclosed how vertical deflection of the structuresdefining channels 27 and outward deflection of the front wall 12 andslice defining assembly 38 has been limited and made independent of thewidth of the box 10 in a construction that provides for stock skimmingand overflow along substantially the entire distance between the rearwall assembly l3 and front wall assembly 12. It should also be notedopen area through the channels 27, 32 can be changed without rebuildingthe box 10, by merely adding or taking away a number of vanes 23 andreplacing the spacers 24, 25, 25a, 33, 33a with new spacers of narroweror wider widths.

From the foregoing detailed description of the present invention it hasbeen shown how the objects of the present invention have been attainedin a preferred manner. However, modification and equivalents of thedisclosed concepts such as readily occur to those skilled in the art areintended to be included in the scope of this invention. Thus, the scopeof the invention is intended to be limited only by the scope of theclaims such as are or may hereafter be, appended hereto.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In an air loaded headbox for a papermaking machine having meansdefining a stock flow chamber between a vertical front wall assembly anda vertical rear wall assembly; a structure defining a stock inletchamber communicating through an opening defined in the rear wallassembly, structure defining a stock outlet chamber with a slice openingand communicating through an opening defined in the front wall assembly,and an assembly of a plurality of parallel and vertical guide vaneshorizontally spaced apart and defining stock flow channels therebetweenwith each vane connected on one end thereof to the rear wall assemblyabove and beneath the opening therein and on the other end thereof tothe front wall assembly above and beneath the opening therein, each saidvanes being generally rectangular and having end portions defined by apair of vertical edges and top and bottom portions defined by a pair ofhorizontal edges, with the upper horizontal edge of adjacent vanesproviding the channels with top portions open upwardly thereof, theimprovement comprising:

a. the vanes defining a first plurality of the channels with endportions open horizontally to provide for horizontal stock flowtherethrough;

b. the vane assembly defining at least one overflow stock channel with abottom portion open in a vertically downward direction to provide forvertically downward stock overflow therethrough;

c. a pair of spacers adjacent a vane defining an overflow stock channelwith each of the overflow channel spacers being adjacent an end portionof the adjacent vane and extending vertically between the top and bottomportions of the adjacent vane to provide end walls for the stockoverflow channel; and

d. a group of three spacers between adjacent vanes defining a horizontalstock flow channel, with a first of the group of spacers being adjacentthe lower horizontal edges of the adjacent vanes and extendinghorizontally between the front and rear wall assemblies and upwardly apredetermined distance to provide a horizontal stock flow channel floor,and the second and third of the group of spacers beinghorizontallyspaced apart with each adjacent an end portion and the top portion ofadjacent vanes.

2. in a headbox according to claim 1, the vane assembly defining aplurality of the stock overflow channels with each stock overflowchannel being between a pair of horizontal stock flow channels andproviding alternate horizontal stock flow channels and stock overflowchannels across the width of the headbox.

3. In a headbox according to claim 1, wherein said means defining thestock flow chamber includes a horizontal structure spaced above the opentop horizontal stock flow channels and overflow channel, with thehorizontal structure defining an enclosed chamber for containingpressurized air for loading paper stock flowing through the open tophorizontal stock flow channels and downwardly through the overflow stockchannel.

4. In a headbox according to claim 1,

a. each vane having a first key projecting vertically upward from eachvane and adjacent the end of the vane at the front wall opening;

b. each vane having a second key projecting vertically upward from eachvane and adjacent the end of the vane at the rear wall opening;

c. a first land connected to the front wall assembly and projectingvertically downward and spaced from the front wall assembly on thechannel side thereof and defining a first vertically extending keyway inthe front wall assembly above the opening therethrough;

d. a second land connected to the rear wall assembly and projectingvertically downward and spaced from the rear wall assembly on thechannel side thereof and defining a second vertically extending keywayin the rear wall assembly above the opening therethrough; and

e. the first key projecting into the first keyway and the second keyprojecting into the second keyway to thereby utilize the vanes to tietogether the front and rear vertical wall assemblies above the openingstherethrough and minimize deflection of the front vertical wall assemblyand slice defining structure.

5. In a headbox according to claim 4, the second and third spacers ofthe group of three spacers and the spacers of the pair of spacers eachhaving a key projecting upwardly and into one of the first and secondkeyways in register therewith and betweenfirst vane keys in the firstkeyway and between second vane keys in the second keyway.

6. In a headbox according to claim 4, a. each .vane having a third keyprojecting vertically downward from each vane and adjacent the end ofthe vane at the front wall opening;

b. each vane having a fourth key projecting vertically downward fromeach vane and adjacent the end of the vane at the rear wall opening;

c. a third land connected to the front wall assembly and projectingvertically upward andspaced from the front wall assembly on the channelside thereof and defining a third vertically extending keyway in thefront wall assembly below the opening therethrough;

d. a fourth land connected to the rear wall assembly and projectingvertically upward and spaced from the rear wall assembly on the channelside thereof and defining a fourth vertically extending keyway in thesecond vertical wall assembly below the opening therethrough; and

e. the third key projecting into the third keyway and the fourth keyprojecting into the fourth keyway to thereby utilize the vanes to tietogether the front and rear vertical wall assemblies below the openingstherethrough and minimize deflection of the front vertical wall assemblyand slice defining structure.

7. In a headbox according to claim-6, the first spacer of the j group ofspacers and the spacers of the pair of spacers each having a keyprojecting downwardly and into one of the third and fourth keyways inregister therewith and between third vane keys in the third keyway andbetween fourth vane keys in the fourth keyway.

8. In a headbox according to claim 6, a a. a fifth keyway defined by afirst horizontal shelf connected to the front wall assembly abovethefront wall opening and projecting toward the stock flow channels todefine the fifth keyway below the first keyway and on to stock outletchamber side of the first keyway;

b. a sixth keyway defined by a second horizontal shelf connected to therear wall assembly above the rear wall opening and projecting toward thefirst shelf to define the sixth keyway below the second keyway and onthe stock inlet chamber side of the second keyway; and

c. each vane having a fifth key projecting into the fifth keyway and asixth key projecting into the sixth keyway to support each of the vanesbetween the front and rear vertical wall assemblies.

9. In a headbox according to claim 8,

a. a seventh keyway defined by a third horizontal shelf connected to thefront wall assembly below the front wall opening and projecting towardthe stock flow channels to define the seventh keyway above the thirdkeyway on the stock outlet chamber side of the third keyway; and

b. an eighth keyway defined by a fourth horizontal shelf connected tothe rear wall assembly below the rear wall opening and projecting towardthe stock floor channels to define the eighth keyway above the fourthkeyway on the stock inlet chamber sideof the fourth keyway; and' c. eachvane having a seventh key projecting into the seventh keyway and aneighth key projecting into the eighth keyway to support each vanebetween the front and rear vertical wall assemblies.

10. In a headbox according to claim 9, the first shelf being connectedto the front wall by an upper front wall member movable upwardlyrelative to the first land and first keyway, a screw operativelyconnected to the movable upper front wall member for raising the firstshelf to lift the fifth vane keys in the fifth keyways and place thevanes in vertical tension between the fifth and seventh vane keyswhenthe headbox is pressurized.

11. In a headbox according to claim 9, the second shelf being connectedto the rear wall by an upper rear wall member movable upwardly relativeto the second land and second keyway, a screw operatively connected tothe movable rear wall member for raising the second shelf to lift thesixth vane keys in the sixth keyways and place the vanes in verticaltension between the sixth and eighth keys when the headbox ispressurized.

12. In a headbox according to claim 11 the third shelf being connectedto the front wall by a lower front wall member movable downwardlyrelative to the third land and third keyway, a screw operativelyconnected to the movable lower front wall member for lowering the thirdshelf to pull the seventh vane key in the seventh keyway to adjustablyhold the vanes in vertical tension between the fifth and seventh vanethe fourth shelf to pull the eighth vane key in the eighth keyway toadjustably hold the vanes in vertical tension between the sixth andeighth vane keys when the headbox is pressurized.

1. In an air loaded headbox for a papermaking machine having meansdefining a stock flow chamber between a vertical front wall assembly anda vertical rear wall assembly; a structure defining a stock inletchamber communicating through an opening defined in the rear wallassembly, structure defining a stock outlet chamber with a slice openingand communicating through an opening defined in the front wall assembly,and an assembly of a plurality of parallel and vertical guide vaneshorizontally spaced apart and defining stock flow channels therebetweenwith each vane connected on one end thereof to the rear wall assemblyabove and beneath the opening therein and on the other end thereof tothe front wall assembly above and beneath the opening therein, each saidvanes being generally rectangular and having end portions defined by apair of vertical edges and top and bottom portions defined by a pair ofhorizontal edges, with the upper horizontal edge of adjacent vanesproviding the channels with top portions open upwardly thereof, theimprovement comprising: a. the vanes defining a first plurality of thechannels with end portions open horizontally to provide for horizontalstock flow therethrough; b. the vane assembly defining at least oneoverflow stock channel with a bottom portion open in a verticallydownward direction to provide for vertically downward stock overflowtherethrough; c. a pair of spacers adjacent a vane defining an overflowstock channel with each of the overflow channel spacers being adjacentan end portion of the adjacent vane and extending vertically between thetop and bottom portions of the adjacent vane to provide end walls forthe stock overflow channel; and d. a group of three spacerS betweenadjacent vanes defining a horizontal stock flow channel, with a first ofthe group of spacers being adjacent the lower horizontal edges of theadjacent vanes and extending horizontally between the front and rearwall assemblies and upwardly a predetermined distance to provide ahorizontal stock flow channel floor, and the second and third of thegroup of spacers being horizontally spaced apart with each adjacent anend portion and the top portion of adjacent vanes.
 2. In a headboxaccording to claim 1, the vane assembly defining a plurality of thestock overflow channels with each stock overflow channel being between apair of horizontal stock flow channels and providing alternatehorizontal stock flow channels and stock overflow channels across thewidth of the headbox.
 3. In a headbox according to claim 1, wherein saidmeans defining the stock flow chamber includes a horizontal structurespaced above the open top horizontal stock flow channels and overflowchannel, with the horizontal structure defining an enclosed chamber forcontaining pressurized air for loading paper stock flowing through theopen top horizontal stock flow channels and downwardly through theoverflow stock channel.
 4. In a headbox according to claim 1, a. eachvane having a first key projecting vertically upward from each vane andadjacent the end of the vane at the front wall opening; b. each vanehaving a second key projecting vertically upward from each vane andadjacent the end of the vane at the rear wall opening; c. a first landconnected to the front wall assembly and projecting vertically downwardand spaced from the front wall assembly on the channel side thereof anddefining a first vertically extending keyway in the front wall assemblyabove the opening therethrough; d. a second land connected to the rearwall assembly and projecting vertically downward and spaced from therear wall assembly on the channel side thereof and defining a secondvertically extending keyway in the rear wall assembly above the openingtherethrough; and e. the first key projecting into the first keyway andthe second key projecting into the second keyway to thereby utilize thevanes to tie together the front and rear vertical wall assemblies abovethe openings therethrough and minimize deflection of the front verticalwall assembly and slice defining structure.
 5. In a headbox according toclaim 4, the second and third spacers of the group of three spacers andthe spacers of the pair of spacers each having a key projecting upwardlyand into one of the first and second keyways in register therewith andbetween first vane keys in the first keyway and between second vane keysin the second keyway.
 6. In a headbox according to claim 4, a. each vanehaving a third key projecting vertically downward from each vane andadjacent the end of the vane at the front wall opening; b. each vanehaving a fourth key projecting vertically downward from each vane andadjacent the end of the vane at the rear wall opening; c. a third landconnected to the front wall assembly and projecting vertically upwardand spaced from the front wall assembly on the channel side thereof anddefining a third vertically extending keyway in the front wall assemblybelow the opening therethrough; d. a fourth land connected to the rearwall assembly and projecting vertically upward and spaced from the rearwall assembly on the channel side thereof and defining a fourthvertically extending keyway in the second vertical wall assembly belowthe opening therethrough; and e. the third key projecting into the thirdkeyway and the fourth key projecting into the fourth keyway to therebyutilize the vanes to tie together the front and rear vertical wallassemblies below the openings therethrough and minimize deflection ofthe front vertical wall assembly and slice defining structure.
 7. In aheadbox according to claim 6, the first spacer of the group of spacersand the spacers of the pAir of spacers each having a key projectingdownwardly and into one of the third and fourth keyways in registertherewith and between third vane keys in the third keyway and betweenfourth vane keys in the fourth keyway.
 8. In a headbox according toclaim 6, a. a fifth keyway defined by a first horizontal shelf connectedto the front wall assembly above the front wall opening and projectingtoward the stock flow channels to define the fifth keyway below thefirst keyway and on to stock outlet chamber side of the first keyway; b.a sixth keyway defined by a second horizontal shelf connected to therear wall assembly above the rear wall opening and projecting toward thefirst shelf to define the sixth keyway below the second keyway and onthe stock inlet chamber side of the second keyway; and c. each vanehaving a fifth key projecting into the fifth keyway and a sixth keyprojecting into the sixth keyway to support each of the vanes betweenthe front and rear vertical wall assemblies.
 9. In a headbox accordingto claim 8, a. a seventh keyway defined by a third horizontal shelfconnected to the front wall assembly below the front wall opening andprojecting toward the stock flow channels to define the seventh keywayabove the third keyway on the stock outlet chamber side of the thirdkeyway; and b. an eighth keyway defined by a fourth horizontal shelfconnected to the rear wall assembly below the rear wall opening andprojecting toward the stock floor channels to define the eighth keywayabove the fourth keyway on the stock inlet chamber side of the fourthkeyway; and c. each vane having a seventh key projecting into theseventh keyway and an eighth key projecting into the eighth keyway tosupport each vane between the front and rear vertical wall assemblies.10. In a headbox according to claim 9, the first shelf being connectedto the front wall by an upper front wall member movable upwardlyrelative to the first land and first keyway, a screw operativelyconnected to the movable upper front wall member for raising the firstshelf to lift the fifth vane keys in the fifth keyways and place thevanes in vertical tension between the fifth and seventh vane keys whenthe headbox is pressurized.
 11. In a headbox according to claim 9, thesecond shelf being connected to the rear wall by an upper rear wallmember movable upwardly relative to the second land and second keyway, ascrew operatively connected to the movable rear wall member for raisingthe second shelf to lift the sixth vane keys in the sixth keyways andplace the vanes in vertical tension between the sixth and eighth keyswhen the headbox is pressurized.
 12. In a headbox according to claim 11the third shelf being connected to the front wall by a lower front wallmember movable downwardly relative to the third land and third keyway, ascrew operatively connected to the movable lower front wall member forlowering the third shelf to pull the seventh vane key in the seventhkeyway to adjustably hold the vanes in vertical tension between thefifth and seventh vane keys, the fourth shelf being connected to therear wall by a lower rear wall member movable downwardly relative to thefourth land and fourth keyway, and a screw operatively connected to thelower movable rear wall member for lowering the fourth shelf to pull theeighth vane key in the eighth keyway to adjustably hold the vanes invertical tension between the sixth and eighth vane keys when the headboxis pressurized.